Typically Ad5 causes upper respiratory tract infections which may manifest as a cold if you’re lucky or lead to pneumonia if you’re not, although things like conjunctivitis and gastroenteritis are not unheard of. Obviously we don’t know how applicable this knowledge is to the Sputnik Ad5.

From the article: "The Ad5 variety has infected a solid proportion of the entire human race [...]. It’s believed that if you already have antibodies and T-cells primed against the Ad5 vector itself (for example) that delivery of its payload will thus be impaired, leading to a less-effective vaccination."