I'll dress up for a party or wedding and ruin my outfit with a pair of flats.
Times, Sunday Times
Hitherto, lanyards have often been considered cumbersome and ugly - in fact, fashion people usually shove them in a handbag rather than deigning to ruin an outfit with them.
Times, Sunday Times
You could even try an undershirt to act as a barrier and catch the sweat before it ruins your outfit.
The Sun