Scrolling through Facebook one day, I came across the meme seen in the header image. The spirit of the meme is very clearly about modesty in our clothing. As with all things, we should be as Christian in our dress sense outside of church as within. There's no point dressing like a Christian for an hour or so on a Sunday if you're just going to dress like trash for the rest of the week.
While the spirit behind the meme is admirable, the point itself falls flat, as there are many clothes which are appropriate for certain non-church settings, yet may seem out of place in an actual church. My MMA/boxing gloves, for example. Why would I sit in the pews looking like I'm about to beat someone up? That would be awkward at best. Yet, when I train Krav Maga, the gloves actually serve a function, namely protecting my hands from damage as I practice punching. Similarly, I would not attend church in swimwear. Even during a baptism, such attire is questionable, but who wants to sit next to a shirtless guy in swim shorts while singing Amazing Grace? Save it for the pool.
In the world today, there are also a number of jobs which require specific clothing. Of course, if you're a police officer coming straight from (or heading straight to) work, that's totally fine. It even feels somewhat comforting to me to see a uniformed officer standing in the pews, because it shows everyone needs salvation, and everyone can receive salvation. A hazmat suit, on the other hand, would serve as quite a distraction.
Interestingly, due to cultural or denominational differences, there are actually very common clothing items I wouldn't wear to specific churches. In some congregations, it may be considered improper for a man to wear a head covering. I, however, wear a bandana whenever I am far enough outside my house. I do not believe it is inappropriate to wear it, and I can actually feel quite uncomfortable if I don't (especially as it serves a practical purpose keeping sweat and other debris out of my eyes), but for sake of my brethren, I would gladly remove it in a church context. Yet, in my congregation, it has never caused an issue.
A particularly interesting example would be coats and jackets. Unless it is particularly cold, I will remove my coat when I get to my chair in church. But as soon as I leave the building, it goes straight back on. This isn't because it's inappropriate to wear a coat. However, as the saying goes, "look like you're staying". If you're a preacher, who would you prefer sitting in front of you? A man who is sat comfortably with his eyes fixed on you, or a man who looks like he's got somewhere else he'd rather be?
So, evidently, there are contexts in which your clothes outside of church may not be appropriate for being inside. But tell me, in any of the above examples, would you be ashamed if your pastor showed up? Do you think a deacon would be embarrassed to catch you in a winter coat? Would an elder scold you for swimming in swimwear?
Now ask that same question about a mankini. Or if you're a woman, a skimpy dress that leaves almost nothing to the imagination. You wouldn't wear these to church because they are wholly inappropriate for any context except the bedroom of a married couple. No one should be able to guess the size of your manhood from a 2 second glance in your general direction. And girls? Your nipples are not the only part of your breasts you should be hiding. There are parts of everyone's body that should only ever be seen by their spouse, or in some cases medical experts/essential caregivers.
As Christians, there are clothes we shouldn't be wearing to Church that we may, and in some cases actually have to wear outside. Mucky boots, smelly overalls, clumsy/noisy PPE, these are all things which may distract from worship and fellowship. Nevertheless, outside church, these things can be anything from appropriate to absolutely necessary. Thus, "would you wear it to church?" is a wholly inadequate standard for judging clothing. But would you be ok if someone from church, especially the leadership, saw you wearing it? If the answer to this question is yes, your conscience is clear. You have committed no sin. But if the answer is no, you may have to ask yourself some very uncomfortable questions.