Liverpool U23 coach Neil Critchley fielded two trialists in Monday's friendly against Panjab FA.
Angel, who is out of contract this summer, is currently on the books at Real Mallorca. Liverpool already have close links with Real Mallorca having loaned them defender Anderson Arroyo earlier this season.
Sinclair is a 17-year-old keeper from St Johnstone and is rated as one of the Scottish club's most talented prospects.
Sanchez scored in the 4-1 win.