If the AirPods case happens to get damaged from your sweat, it costs $60 to replace the normal case, and $70 for the new wireless case that launched this year.
Other active headphones and earbuds do a better job at creating a seal around your ear to limit background noise. I personally recommend Master & Dynamic's MW07's if you want wireless earbuds, since those are advertised as "splash-resistant."
If you prefer wireless over-ear headphones for working out like I do, you'll love Urbanears' Hellas, which only cost $60.
Even more exercise-friendly AirPods alternatives are on the horizon, like Beats' Powerbeats Pro, and JBL's Endurance Peak.