notadictionary.com
怪しげな栄養剤を飲んでいる人が、「これ効きますよ。
→ “A person drinking some suspicious supplement says, 'This works!'”
怪しげな ayashigena = suspicious (adjective)
怪 aya = strange / mysterious
しげな shigena = resembling / full of
栄養剤 eiyouzai = nutrient supplement (noun)
栄養 eiyou = nutrition / nourishment
剤 zai = agent / preparation
を o = (particle) marks the direct object
飲んでいる nondeiru = drinking (verb - te-form + iru for ongoing action)
人 hito = person (noun)
が ga = (particle) marks the subject
「 " = (punctuation) opening quotation mark
これ kore = this (pronoun)
効きます kikimasu = works / is effective (verb)
よ yo = (particle) adds emphasis or assertion
」 " = (punctuation) closing quotation mark