Three men attempted to steal £20,000 worth of mobile phones from Tesco on Jane Murray Way.
The men attempted to rip the devices from the display alerting staff, customers and off duty police officers on 17 May.
The defendants were arrested and charged with attempted robbery, and all pleaded guilty.
Valetin Bocan was sentenced at Lewes Crown Court to 23 months’ imprisonment, Mario Ilie was sentenced to 22 months - suspended for 24 months and a 16 year old boy was referred to a youth offender panel.
Detective Constable Stuart MacPherson said: “This was a brazen act of attempted robbery, committed in a busy supermarket in broad daylight.
“The defendants seemingly had no concern for the consequences of their actions, and it is only thanks to the quick-thinking staff, customers and off-duty officers that they were detained and a significant loss was prevented.”