Most Helpful Guy
Don't stop wearing Nike. They're just picking on you, and they chose the brand you usually wear to do it. Stop caring, or play along; tease them back. If they see you don't care what they say, they may stop saying it, or just treat it as a joke. If they see you care, they'll use it against you.
Most Helpful Girl
Everybody gets comments about what they wear. You get comments about wearing Nike because that sounds like what you wear most of the time. I get comments about somebody dying or being depressed because I wear black most of the time. I used to get comments about the purple sweater I wore every single day in middle school, but also got comments about now wearing it when I took it off for a couple of days in the spring. Basically people are just going to come up with comments about whatever you wear even if you change it. If you stop wearing Nike and switch to Lululemon, they'll call you the Lululemon girl. I wouldn't suggest switching to another name brand because you'll get the same reaction
However if the being spoiled and rich bitch comments are bothering you, consider switching to generic brands that Walmart, Old Navy, and Target stores carry. Nike is a name brand and name brands are considered to be luxurious for rich people. If you want to stop those comments, you'll have to stop "flaunting" brands on your clothing. I often shop at thrift store or discount stores that carry name brands at decent prices, but mostly wear off-brand clothing, so I never get comments about the brands I wear