With clear history, no further work up is indicated
With altered mental status or ambiguous presentation consider:
Urinalysis, CBC, BMP, LFTs
CT head
tox workup
infectious work up
Urinalysis, CBC, BMP, LFTs
CT head
tox workup
infectious work up
Caffeine toxicity
Cocaine
Nicotine toxicity
Amphetamines
Clenbuterol toxicity
Synthetic cathinones 
Ipecac toxicity
Ketamine