this can mean a variety of things, mostly used in a bar/club atmosphere; or joking with your friends:
ima make you sweat
ima break you off
ima get you wet
get everything ready
you can also say this to someone who is excited
also it doesnt have to be just napkins...you can use name brands also...
"doggie, we gonna pull hella bitches at the club tonight"
" yea nigga get your napkins ready"
"yo man, tell me the truth is there gonna be hella bitches at the party?"
"yea nigga you better bring a bounty roll with you, shit...better buy bulk from costco or somethin!"